Mechanism to transfer engine torque and control motion across helicopter rotor vibration isolator

ABSTRACT

A helicopter rotor is attached to a structural member which is in turn mounted on an airframe by vibration isolators which enable the rotor and structural member to vibrate in a vertical plane and do not transmit these vibrations to the airframe. A linkage system having one bell crank pivoted on the structural member and another bell crank pivoted on the airframe is used to transfer control motion to the helicopter rotor with a minimum of interference from the vibration of the rotor and structural member. Universal joints are used to transfer engine torque from the engine mounted on the airframe to the vibrating rotor.

United Stat es Patent James E. Dueweke Alexandria, Va.

Jan. 15, 1969 Feb. 16, 1971 The United States of America, as representedby the Secretary of the Navy [72] Inventor [21 Appl. No. [22] Filed [451 Patented [73] Assignee [54] MECHANISM TO TRANSFER ENGINE TORQUE ANDCONTROL MOTION ACROSS HELICOPTER 17.25, 17.11;416/168, 159, 131;74/497,496, 491, 469; 248/(lnquired) 2,506,960 5/1950 Hensley 74/4692,739,769 3/1956 Rogers 244/17.27 2,761,635 9/1956 Hiller, Jr. et al.244/1 7.27 3,095,931 7/1963 Peiffer et al. 416/159X 3,163,378 12/1964Balke et al. 244/17.27 3,199,601 8/1965 Dean et a1 74/469X FOREIGNPATENTS 1,009,222 3/1952 France 244/17.27

Primary Examiner-Milton Buchler Assistant Examiner-Paul E. SaubererAnrneys-- Edgar J. Brower, Arthur L. Branning and Thomas 0. Watson, Jr.

ABSTRACT: A helicopter rotor is attached to a structural member which isin turn mounted on an airframe by vibration isolators which enable therotor and structural member to vibrate in a vertical plane and do nottransmit these vibrations to the airframe. A linkage system having onebell crank pivoted on the structural member and another bell crank I[56] References Cited pivoted on the airframe is used to transfercontrol motion to UNITED STATES PATENTS the helicopter rotor with aminimum of interference from the 2,318,260 /1943 Sikorsky 244/ 17.25UXvibration of the rotor and structural member. Universal joints 2,385,88110/1945 Peterson... 244/17.25UX are used to transfer engine torque fromthe engine mounted 2,428,200 9/ 1947 Campbell 244/1 7.25UX on theairframe to the vibrating rotor.

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MECHANISM TO TRANSFER ENGINE TORQUE AND CONTROL MOTION ACROSS HELICOPTERROTOR VIBRATION ISOLATOR STATEMENT OF GOVERNMENT INTEREST The inventiondescribed herein may be manufactured and used by or for the Governmentof the United States of Americe for governmental purposes without thepayment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to rotor drives and controls and, more particularly, to meansfor transferring 'drive and control motion to a vibrating rotor with aminimum of interference from the vibration.

2. Description of the Prior Art In the prior art various arrangementshave been devised to minimize the effect of helicopter rotor vibrationupon the helicopter airframe. For a discussion of the problem andvarious proposed solutions the following U.S. Pat. Nos. may beconsulted: 2,615,657 to Young et al., 3,163,378 to Balke et al.;3,298,443 to Burkam et al. and 3,322,379t Flannelly. The solutionsproposed normally involve interposing a vibration absorbing orcompensating system between the helicopter airframe and the rotorassembly.'This means that the rotor will vibrate relative to theairframe.

In order to control the helicopter, the pitch of the rotor blades arevaried by a control rod which is operated from the pilot's compartmentof the helicopter and extends normally to a swash plate which is mountedon the helicopter rotor shaft and connected to the rotor blades. Whenthe control rod is operated the swash plate is moved axially of and/ortitled relative to the rotor shaft and thereby changes the pitch of therotor blades. If, as with the above-mentioned vibration insulatingarrangements, the rotor assembly and swash plate vibrate relative to thehelicopter, it can be seen that the positioning and movement of thecontrol rod and therefore the pitch of the rotor blades will beinfluenced by the rotor vibration. Further, if the helicopter engine ismounted on the helicopter airframe, it can be seen that it is difficultto transmit rotary motion to the vibrating rotor shaft.

SUMMARY OF THE INVENTION This invention solves the abovementionedproblems by providing a linkage arrangement for transmitting rotor pitchcontrol motion which minimizes the effect of vertical vibrations of thehelicopter rotor relative to the helicopter body. Further, a means fortransferring engine torque from the helicopter airframe to the vibratinghelicopter rotor is provided.

OBJECTS OF THE INVENTION It is an object of the present invention toprovide a control system for a rotor which minimizes the effect of rotorvibration upon the control.

Another object of the present invention is to provide a system forcoupling an engine for transmitting torque to a vibrating rotor.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows schematically the controllinkage and power coupling of the instant inventionjand FIG. 2 shows howthe linkage of the present invention minimizes the effect of rotorvibration on control motion.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a portion of ahelicopter, designated generally by reference numeral 11 and includingan airframe 12. A structural member M is attached to the airframe bymeans of vibration isolators 15. The vibration isolators can be of anyknown type which allows the rotor assembly to vibrate primarily only ina direction longitudinal of said rotor shaft and form no part of thisinvention. Among the vibration isolators that could be used are theDynamic Antiresonant Vibration Isolator and the Gyroscopic VibrationAbsorber," both manufactured by Kaman Aircraft and the ElectrohydraulicVibration Isolator manufactured by Barry Controls. A thrust bearing 16on the member 14 is used to rotatably connect a rotor shaft I7 to theairframe 12 Mounted for axial and/or tilting displacement on the rotorshaft is a swash plate 18 pivotally interconnected with a rotor blade 19by a pitch link 20. By moving the swash plate axially of the rotor shaft17 and/or tilting it the pitch of rotor blade 19 is varied. The swashplate-pitch link arrangement is shown schematically since it forms nopart of the invention. Any similar arrangement known in the art could beused.

In order to move the swash plate axially of the rotor shaft and/or tiltit a pitch control linkage is provided, designated generally byreference numeral 21. The linkage is made up of a rod 22 extendinggenerally in the direction of vibratory motion of the rotor assemblyhaving one end connected to the swash plate 18 and pivoted at its otherend to one end 24 of a bell crank 23. Bell crank 23 is pivoted onstructural member 14 at a point 25. Pivoted to the other end 26 of bellcrank 23 is a rod 28 which extends substantially perpendicular to rod22. The other end of rod 23 is pivoted toone end 29 of a bell crank 27.Bell crank 27 is pivoted to the helicopter airframe 12 at a point 30.Pivoted to the other end 3ll of bell crank 27 is a rod 32 which, asshown, extends substantially parallel to rod 22, but can actually extendin any desired direction in which it can be used to pivot bellcrankabout point 30. Rod 32 can be actuated to move lengthwise throughvarious known mechanisms by the pilot of the helicopter. This lengthwisemovement of rod 32 is transmitted through the control linkage to swashplate 1B which in turn varies the pitch of helicopter rotor blade 19.

Because of the vibration isolators, member 14 and the helicopter rotorvibrate relative to the helicopter in a direction axial of rotor shaftll7. Generally, the total amount of displacement of member 14 relativeto the airframe is approximately one-half of an inch. It can be seenthat if a control rod extended directly from the swash plate to thepilot's compartment on the airframe the full amount of vibratory motionof the rotor assembly relative to the airframe would be transmittedthrough the control rod to the controls operated by the pilot, thusmaking such control of the helicopter rotor uncertain and inaccurate.

An analysis of FIG. 2 will show how the linkage of the present inventionovercomes the above problem. Since the total amount of verticalvibration movement is 0.5 inch, end 26 of rod 28 will vibrateup-and-down around a zero point a distance A of 0.25 inch. If we assumethat rod 28 is 3 feet long, the total effect of the vibrational movementon the linkage system, represented by the distance B, is approximately0.001 inch. It can be seen that if there were a direct controlconnection from the vibrating rotor assembly to the pilot's cabin, avertical displacement of the rotor assembly of 0.25 inch would cause acorresponding displacement of the control rod. However, with Applicantslinkage system a 0.25 inch displacement the rotor system introduces onlya 0.001 inch displacement of the control rod system. In a linkage systemsuch as that shown by Applicant, a 0.001 inch displacement of a controlrod system is negligible since the linkage has more play in it thanthat. It can be seen that the longer rod 28 the less influence thevibration of the rotor assembly relative to the helicopter body willhave.

It is clear that the effect of transverse vibration of member 14 willnot be eliminated by the linkage system shown. However, with most knownvibration isolation systems the vibration of the rotor is confined to avertical direction and the transverse vibration of the rotor assembly isnegligible.

As shown schematically in FIG. 1, an engine 34 and a transmission 35 aremounted on the helicopter airframe. Rotary motion is transmitted to therotor shaft 17 by a drive shaft 36. In order to effectively transmitthis rotary motion to the vibrating rotor shaft, universal joints 38 and39 are provided. At the junction between the drive shaft and the rotorshaft a bevel gear assembly 40 is provided. With one universal jointbeing disposed in the drive shaft adjacent the airframe and one adjacentthe vibrating member 14 it is possible to transmit rotary motion to thevibrating rotor shaft 17.

Many alterations and modifications may be made in light of the aboveteachings. For example, Applicants concept is not limited to use inhelicopters but can be used in any environment where a vibrating rotorassembly must be driven from a stationary motor or motion must betransmitted from a stationary position to vibrating position withoutinterference from the vibrations.

lclaim:

l. A system for transmitting motion from a relatively stationary body toa body vibrating primarily in one direction while minimizing the effectsof the relative vibration on the motion transmitted, the direction ofmotion transmitted being in the direction ofvibration, said systemcomprising:

a first rod;

a first bell crank pivoted to said relatively stationary body, saidfirst rod having one end pivoted to one end of said first bell crank;

a second rod having one end pivoted to the other end of said first bellcrank;

a second bell crank pivoted to said vibrating body, said second rodhaving its other end pivoted to one end of said second bell crank; and

third rod pivoted to the other end of said second bell crank andextending in a direction generally perpendicular to said second rod, thedirection of said third rod extension further being the direction ofprimary vibratory movement of said vibrating body, whereby longitudinalmotion imparted to said first rod is transmitted to said third rod withminimum effect from the vibration of said vibrating body.

2. The system of claim 1 wherein the other end of said first rod isconnected to a helicopter control member and the other end of said thirdrod is connected to means for varying the pitch of a helicopter rotorblade.

3. In a helicopter, the combination comprising:

a helicopter airframe;

a rotor assembly including adjustable pitch rotor blades;

vibration isolating means for isolating vibrations of said rotorassembly so that they are not transmitted to said airframe;

a control member for transmitting motions from said airframe to saidrotor blades;

means responsive to said control member for varying the pitch of saidrotor blades;

a first rod connected to and moveable lengthwise by said control member;

a second rod extending in the direction of primary vibratory rotormotion and connected to said pitch varying means for actuation thereofby lengthwise movement of said second rod; and

a third rod perpendicular to said second rod and connected to said firstand second rods by first and second bellcranks, respectively, said firstbellcrank being pivoted to said body and second bell crank to saidisolated rotor assembly.

1. A system for transmitting motion from a relatively stationary body toa body vibrating primarily in one direction while minimizing the effectsof the relative vibration on the motion transmitted, the direction ofmotion transmitted being in the direction of vibration, said systemcomprising: a first rod; a first bell crank pivoted to said relativelystationary body, said first rod having one end pivoted to one end ofsaid first bell crank; a second rod having one end pivoted to the otherend of said first bell crank; a second bell crank pivoted to saidvibrating body, said second rod having its other end pivoted to one endof said second bell crank; and a third rod pivoted to the other end ofsaid second bell crank and extending in a direction generallyperpendicular to said second rod, the direction of said third rodextension further being the direction of primary vibratory movement ofsaid vibrating body, whereby longitudinal motion imparted to said firstrod is transmitted to said third rod with minimum effect from thevibration of said vibrating body.
 2. The system of claim 1 wherein theother end of said first rod is connected to a helicopter control memberand the other end of said third rod is connected to means for varyingthe pitch of a helicopter rotor blade.
 3. In a helicopter, thecombination comprising: a helicopter airframe; a rotor assemblyincluding adjustable pitch rotor blades; vibration isolating means forisolating vibrations Of said rotor assembly so that they are nottransmitted to said airframe; a control member for transmitting motionsfrom said airframe to said rotor blades; means responsive to saidcontrol member for varying the pitch of said rotor blades; a first rodconnected to and moveable lengthwise by said control member; a secondrod extending in the direction of primary vibratory rotor motion andconnected to said pitch varying means for actuation thereof bylengthwise movement of said second rod; and a third rod perpendicular tosaid second rod and connected to said first and second rods by first andsecond bellcranks, respectively, said first bellcrank being pivoted tosaid body and second bell crank to said isolated rotor assembly.